The GRBAlpha nanosatellite observed the most powerful cosmic explosion since the beginning of human civilisation

On Sunday, Oct. 9, 2022, a pulse of intense radiation swept through the solar system so exceptional that astronomers quickly dubbed it the BOAT – the brightest of all time. The source was a gamma-ray burst (GRB), the most powerful class of explosions in the universe. The burst triggered detectors on numerous spacecraft, and observatories around the globe and was also observed by the world's smallest astrophysical satellite, GRBAlpha.

28 Mar 2023 Tereza Fojtová

This illustration shows the ingredients of a long gamma-ray burst, the most common type. The core of a massive star (left) has collapsed, forming a black hole that sends a jet of particles moving through the collapsing star and out into space at nearly the speed of light. Radiation across the spectrum arises from hot ionized gas (plasma) in the vicinity of the newborn black hole, collisions among shells of fast-moving gas within the jet (internal shock waves), and from the leading edge of the jet as it sweeps up and interacts with its surroundings (external shock). Credit: NASA's Goddard Space Flight Center

The analysis of the data from this nanosatellite is led by the High Energy Astrophysics research group in the Department of Theoretical Physics and Astrophysics at the Faculty of Science of Masaryk University (MU).The GRB detector development and final satellite integration were led by Konkoly Observatory in Hungary, which together with the Faculty of Aeronautics of the Technical University of Košice, Slovakia and MU also operates the satellite.

Gamma-ray bursts are produced by collisions of neutron stars or gravitational collapses of very massive, rapidly rotating stars, and present an opportunity for astrophysicists to elucidate and demonstrate a range of physical phenomena.

Credit: Pál et al. 2023/GRBAlpha collaboration

"While instruments on large NASA satellites such as the Fermi Gamma-ray Observatory were overwhelmed by the extreme brightness of this source and were unable to measure its maximum brightness, GRBAlpha, with its relatively small and technically innovative detector, was able to measure the brightness of the flare even at its maximum, and thus contributed to the research of this extraordinary phenomenon," said Jakub Řípa from Department of Theoretical Physics and Astrophysics at the Faculty of Science of Masaryk University (MU), the first author of the article presenting the results in the journal Astronomy and Astrophysics. Astronomers have thus managed to estimate how much energy is released and radiated away after a star turns into a black hole.

The big and the small one. When Fermi and GRBAlpha detected the burst, the Neil Gehrels Swift Observatory was on the other side of the Earth and localized the burst an hour later thanks to its afterglow. Credit:  > Francis Reddy/NASA Goddard, University of Maryland

"GRBAlpha has proven that even small satellites can provide important observations and effectively complement the work of large space missions," said Filip Münz, an astrophysicist and co-author of the article from MU's Faculty of Science. The nanosatellite, which celebrated two years of successful operation in orbit on 22 March 2023, is the result of a collaboration between Hungarian, Czech, Slovak and Japanese scientists. "So far, it has recorded 42 events, including 27 gamma-ray bursts, 12 solar flares, two magnetar bursts and one X-ray binary flare," said Marianna Dafčíková, an astronomy student at the Faculty of Science at MU and co-author of the article, who is a major contributor to the operation and data analysis of the satellite.

GRB 221009A appeared in the constellation Sagitta, within the dust-rich central plane of our galaxy. The bright star at upper left is Vega. Credit: NASA’s Goddard Space Flight Center

Other countries and institutions are developing similar nanosatellites, but GRBAlpha is the first of its kind and opens the way for other projects," emphasised Norbert Werner, head of the High Energy Astrophysics research group at the Faculty of Science of MU and co-initiator of the project.

The signal from GRB 221009A had been traveling for about 1.9 billion years before it reached Earth, making it among the closest-known “long” GRBs, whose initial, or prompt, emission lasts more than two seconds. Astronomers think these bursts represent the birth cry of a black hole that formed when the core of a massive star collapsed under its own weight. As it quickly ingests the surrounding matter, the black hole blasts out jets in opposite directions containing particles accelerated to near the speed of light. These jets pierce through the star, emitting X-rays and gamma rays as they stream into space.

“GRB 221009A was likely the brightest burst at X-ray and gamma-ray energies to occur since human civilization began,” said Eric Burns, an assistant professor of physics and astronomy at Louisiana State University in Baton Rouge. He led an analysis of some 7,000 GRBs – mostly detected by NASA’s Fermi Gamma-ray Space Telescope and the Russian Konus instrument on NASA’s Wind spacecraft – to establish how frequently events this bright may occur. Their answer: once in every 10,000 years.

More details:

XMM-Newton images captured 20 dust rings, 19 of which are shown here in arbitrary colors. The image merges observations made two and five days after GRB 221009A erupted. Dark stripes indicate gaps between the detectors. A detailed analysis shows that the widest ring visible here, comparable to the apparent size of a full moon, came from dust clouds located about 1,300 light-years away. The innermost ring arose from dust at a distance of 61,000 light-years – on the other side of our galaxy. GRB22
X-rays from the initial flash of GRB 221009A could be detected for weeks as dust in our galaxy scattered the light back to us. This resulted in the appearance of an extraordinary set of expanding rings. Images captured over 12 days by the X-ray Telescope aboard NASA’s Neil Gehrels Swift Observatory, shown here in arbitrary colors, were combined to make this movie.  Credit: NASA/Swift/A. Beardmore (University of Leicester)

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